Physics · Semiconductor Electronics : Materials, Devices And Simple Circuits · NEET
Minority carriers only. In reverse bias, the applied field pushes majority carriers AWAY from the junction, so they cannot cross. But minority carriers (electrons in the p-side, holes in the n-side) are pushed TOWARD the junction and cross easily. That is why the reverse current is very small (microamps) and is carried by minority carriers. NEET 2024 tested exactly this and marked 'due to majority carriers' as wrong.
Because it is limited by how MANY minority carriers exist, not by the voltage. Even a small reverse voltage is already enough to sweep across every minority carrier that reaches the junction. Adding more voltage cannot create extra minority carriers, so the current stays almost flat (saturated) until breakdown. NCERT says: the current is 'not limited by the magnitude of the applied voltage but is limited due to the concentration of the minority carriers'.
Breakdown voltage is the critical reverse voltage at which the reverse current suddenly increases very sharply, even though the diode was passing almost no current before. Below it, current is a flat tiny I0. At the breakdown voltage the curve drops steeply downward on the V-I graph. A Zener diode is built to work safely in this breakdown region and is used as a voltage regulator.
Microamps (uA), sometimes even nanoamps. It is tiny compared to forward current, which is in mA. If a question says the reverse current is 'measured in uA', that is a hint they are talking about the reverse saturation current from minority carriers. NEET 2024 used the phrase 'current measured in uA'.
Yes. Heating a semiconductor breaks more covalent bonds and creates more electron-hole pairs, so the number of minority carriers goes up. More minority carriers means a larger reverse saturation current. This is why NEET 2018 marked 'heating affects the overall V-I characteristics' as correct, not just the forward side.
Consider the following statements A and B and identify the correct answer: A. For a solar cell, the I-V characteristic lies in the fourth (IV) quadrant of the graph. B. In a reverse biased p-n junction diode, the current measured in uA is due to majority charge carriers.
Two statements are given: A. When the forward bias voltage across a p-n junction diode increases above a certain threshold voltage, the diode current increases significantly. B. This current is called reverse saturation current. Choose the correct answer.
Statement I: Photovoltaic devices can convert optical radiation into electricity. Statement II: A Zener diode is designed to operate under reverse bias in the breakdown region.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the tiny reverse-bias current (a few microamps) carried by minority carriers, which stays almost constant no matter how much you raise the reverse voltage, up to breakdown.
Because it saturates, meaning it becomes flat and does not increase with voltage. It is set by the number of minority carriers available, not by the applied reverse voltage.
It is usually written as I0 (or Is). It appears in the diode equation I = I0 (e^(V/nVT) - 1).
No. Knee/threshold voltage is a small FORWARD voltage (about 0.3 V for Ge, 0.7 V for Si) where forward current starts rising. Breakdown voltage is a REVERSE voltage where reverse current suddenly shoots up.
Not always. An ordinary diode can be damaged by excess heat, but a Zener diode is specially made to work safely in the breakdown region and is used as a voltage regulator.
Heat creates more electron-hole pairs, so more minority carriers are available to cross the junction, which increases I0.
